A visitor to Yellowstone National Park is dead after an encounter with a grizzly bear Wednesday morning.

The incident occurred on the Wapiti Lake trail, which is located east of the Grand Loop Road south of Canyon Village.

The husband and wife couple had traveled about a mile and a half in on the trail Wednesday morning when they surprised a grizzly sow with cubs. In an apparent attempt to defend a perceived threat to her cubs, the bear attacked and fatally wounded the man. Another group of hikers nearby heard the victim’s wife crying out for help, and used a cell phone to call 911. Park rangers were summoned and quickly responded to the scene.

“It is extremely unfortunate that this couple’s trip into the Yellowstone backcountry has ended in tragedy,” said Dan Wenk, Superintendent of Yellowstone National Park. “Our heart goes out to the family and friends of the victim as they work to cope with their loss.”

The name and hometown of the victim are being withheld pending notification of family members.

Attacks by bears are extremely rare. No visitors were injured by bears in the park in 2010. This is the first bear-caused human fatality in Yellowstone since 1986.

Patrols are underway to clear the area of all backcountry users. All trails and backcountry campsites in the area have been closed until further notice. The incident is under investigation.

A bear warning sign is posted at the Wapiti Lake trailhead, since it is one of the access points to the Pelican Valley area, known for significant bear activity. However, there had been no reports of bear encounters along or near the Wapiti Lake trail this season. There had been no recent reports of animal carcasses along or near the trail. No research trapping of bears has been conducted in Yellowstone National Park this season.

Park visitors are advised to stay on designated trails, hike in groups of three or more people, and to be alert for bears and make noise in blind spots. Bear pepper spray has been highly successful at stopping aggressive behavior in bears. It is not yet known if either individual involved in this attack was carrying bear pepper spray.

Hikers and backcountry users are encouraged to check with staff at park visitor centers or backcountry offices for updated information before planning any trips in the Canyon area. Updated information is also available by calling 307-344-2160 during normal business hours.